The present invention relates to the control of data network access servers and in particular, though not necessarily, to the control of network access servers connecting subscribers of a telecommunications network to a data network.
Access to the Internet, and in particular to the World Wide Web (WWW), is usually obtained via a telecommunication network to which a user subscribes, the user interface being a Personal Computer (PC) or the like. The telecommunication network provides the user with a reserved telephone line (or rather channel) to a Network Access Server (NAS) operated by an Internet Service Provider (ISP), and a so-called Point-to-Point Protocol (PPP) connection is established between the user and the NAS. The NAS provides the user with an Internet Protocol (IP) address and acts as a protocol converter between the circuit switched transmission protocol of the telecommunications network (typically E.1 or T.1) and the packet switched Internet Protocol (usually TCP/IP).
The Network Access Servers (NAS) enable the operator of a telecommunications network to connect its subscribers directly to the WWW without the need for an external ISP. Typically, several NAS are connected to an exchange of the telecommunications network and provide functionality similar to that provided by conventional IAS. The advantage of the NAS approach is that subscribers may be charged for telephone connections and WWW access in a single bill issued by the telecommunications network. It follows that a subscriber may be billed relatively small amounts for WWW access, which could otherwise not be billed in an economical manner.
In the case of the E.1 or T.1 telecommunications network transmission protocol, a signalling protocol known as Signalling System 7 is commonly used to establish, maintain, and terminate circuit switched channels between various components of a telecommunications network. In particular, SS7 is used to control the channel between the local exchange of a subscriber, any intermediate or transit exchanges, and an IAS allocated to the subscriber. SS7 occupies one time slot per frame of the Time Division Multiple Access (TDMA) E.1 or T.1 transmission protocols (the other slots being available for user data).
SS7 makes use of addresses known as Point Codes to route signalling data through the xe2x80x9cvisibility areaxe2x80x9d of a telecommunications network, the visibility area typically being the network itself together with the interfaces between the network and xe2x80x9cforeignxe2x80x9d networks under the control of other operators. A Point Code is placed in the header of a signalling packet and is examined by an exchange upon receipt of the packet to determine the next hop for the packet en route to its destination.
SS7 provides for a 12 bit Point Code, i.e. 4096 possible unique addresses. This has been sufficient for conventional networks having a relatively small number of exchanges. However, with the introduction of IASs, each of which requires its own Point Code within a network""s visibility area, it is likely that 4096 Point Codes will be insufficient.
It is an object of the present invention to provide a communications network in which the above noted disadvantage is overcome or at least mitigated.
It is a second object of the invention to provide a communications network comprising data network access servers and in which each access server does not necessarily require its own signalling address within the communications network.
According to a first aspect of the present invention there is provided a method of signalling in a telecommunications network to control a set of circuit switched channels between a network exchange and a data network access server (NAS), the method comprising:
transmitting signalling data between the exchange and a gateway node using a circuit switched transmission protocol, the exchange and the gateway node being assigned respective Point Code addresses under said circuit switched transmission protocol;
transmitting signalling data between the data NAS and the gateway node using a packet switched transmission protocol, the gateway node and the NAS being assigned respective addresses under said packed switched transmission protocol;
providing a look-up table at the gateway node mapping the NAS packet switched transmission protocol address to the exchange Point Code address and a set of identifiers corresponding to said set of channels; and
receiving signalling data at the gateway node from the exchange, and routing the data to the NAS using the packet switched transmission protocol address for the NAS obtained from said look-up table using the Point Code address of the source exchange and a channel identifier conveyed with the signalling data.
Embodiments of the present invention have the advantage that signalling data is routed to a data network access server using a data network address rather than a telecommunications network signalling protocol address. Thus the number of network access servers which can be used within the visibility area of the telecommunications network is significantly increased. Furthermore, it is possible to share a data network interface of the network access server for both signalling purposes and for accessing the data network itself, i.e. there is no need to provide a separate, dedicated signalling interface at the network access server.
It is envisaged that the main application of the present invention will be the connection of subscriber terminals to the Internet (and more particularly to make use of the World Wide Web (WWW)), where said packet switched signalling protocol is Internet Protocol (IP), and said data network addresses assigned to the gateway node and to the data network access server are IP addresses. Signalling data may be transmitted between the gateway node and the network access server via the WWW or via a closed connection such as a data bus connecting the exchange to the network access server.
It is also envisaged that the invention may be used to provide connections to data networks other than the WWW, for example Local Area Networks (LANs) and Wide Area Networks (WANs) in which the Signalling protocol may be IP or some other protocol.
In a preferred embodiment of the present invention, the circuit switched signalling protocol of the telecommunications network is Signalling System 7 (SS7).
Preferably, said gateway node is coupled to a plurality of exchanges, each exchange being coupled in turn to a set of NASs. Said look-up table then contains a list of the NAS packet switched transmission protocol addresses and, for each such address, the Point Code address of the associated exchange and the channel identifiers of the channels between the NAS and the exchange.
According to a second aspect of the present invention there is provided apparatus for controlling a set of circuit switched channels between a network exchange and a data network access server (NAS), the apparatus comprising:
a gateway node coupled between the NAS and the exchange;
first transmitting means for transmitting signalling data between the exchange and the gateway node using a circuit switched transmission protocol, the exchange and the gateway node being assigned respective Point Code addresses under said circuit switched transmission protocol;
second transmitting means for transmitting signalling data between the data NAS and the gateway node using a packet switched transmission protocol, the gateway node and the NAS being assigned respective addresses under said packed switched transmission protocol; and
data storage means at or coupled to the gateway node and providing a look-up table mapping the NAS packet switched transmission protocol address to the exchange Point Code address and a set of identifiers corresponding to said set of channels,
wherein the gateway node is arranged in use to receive signalling data from the exchange, and to route the data to the NAS using the packet switched transmission protocol address for the NAS obtained from said look-up table using the Point Code address of the source exchange and a channel identifier conveyed with the signalling data.
According to a third aspect of the present invention there is provided a gateway node of a telecommunications network, the gateway node being arranged to route signalling data to control a set of circuit switched channels between a network exchange and a data network access server (NAS), the gateway node comprising:
first input/output means for communicating signalling data between the gateway node and the exchange using a circuit switched transmission protocol, the exchange and the gateway node being assigned respective Point Code addresses under said circuit switched transmission protocol;
second input/output means for transmitting signalling data between the gateway node and the NAS using a packet switched transmission protocol, the gateway node and the NAS being assigned respective addresses under said packed switched transmission protocol;
data storage means providing a look-up table mapping the NAS packet switched transmission protocol address to the exchange Point Code address and a set of identifiers corresponding to said set of channels; and
routing means for routing signalling data received from the exchange to the NAS using the packet switched transmission protocol address for the NAS obtained from said look-up table using the Point Code address of the source exchange and a channel identifier conveyed with the signalling data.